Jim Gollan @ OCA Art of Photography: Intensity of Light - Higher and Lower Sensitivity (4.1b)

Requirement

At least 12 images, 6 scenes x High/Low ISO

Purpose

To understand the trade-off in low light of using either low or high ISO: desired exposure vs. higher levels of noise

Technical Learning

Most cameras are designed so that they can capture sharply at ISO 100 people walking in average daylight, when handheld (shutter speed of at least 1/125 sec) using an aperture producing acceptable depth of field (say, f5.6)
As light reduces from this level, some adjustment is needed (i.e. ISO, shutter speed or aperture)
Increasing ISO, say from 100 to 400, is an EV4.0 change, enabling either shutter speed to be 4 times faster (reducing motion blur) or aperture to be 4 times narrower (lengthening depth of field), or some combination of both
However, the price for using higher ISO is the increased risk of noise

Noise

It is a sampling error where less than an ideal level of light reaches the sensor producing a random pattern of aberrant pixels, typically of varying brightness (luminance) and colour (chrominance)
It is usually most evident in areas of continuous tone and deep shadow
Its impact depends on the size at which the image is viewed, i.e. the larger the more noticeable it becomes
It is the opposite of 2 other effects: 'blooming' (flare around blown highlights) and chromatic aberration (highlights with either a red-cyan or blue-yellow fringe)

Exercise Instructions

Shoot 6 scenes first at ISO 400/800 where motion and/or depth of field may be at the margin of acceptability, then shoot the same scene at ISO 100. What impact did the higher ISO setting have?
Examine areas of flat tone and deep shadow in each image for signs of noise in close-up
Consider to what extent noise matters in these images

Images and Review

Used the spinning wheel of my wife's bicycle in the dimly lit garage to conduct this test.

Lumix DMC G3